Folder/file sharing: i have two computers at home with a shared internet connection(via a switch)?

how do i share a folder from HOMEPC1 to my office pc(shared connection via gateway)?

i have two home computers. and there are two internal ip addresses and one external ip...

how would it know if the shared folder is from HOMEPC1 or HOMEPC2?

Turn on windows file and printer sharing, under your NIC settings. Turn off or allow file sharing in your firewalls on each computer. Go to each computer and SHARE someting (right click the target folder, printer, ect., and go to the sharing options). To make things easier, put both computers in the same workgroup...then just go to network neighborhood, or go to Start > Run and type in
\\computername\sharename
you and also use the IP address instead of "computername"...of course, substitue the computer name for "computername" :)

Make sure both computer are in the same workgroup. For XP, do this by right clicking on My Computer, then properties. Click Computer Name Tab.
To share the folder, right click on folder, then click sharing and security. Click the check box, share this folder on the network. Then give it a share name. If you want to read and write to the files you will have to click the other check box, allow network users to change my files.

From the other computer now you can just go to My Network Places it should give you a list of all the shared folders. you can even map to that folder by opening My Computer, Tools, Map Network Drive. Select a drive letter, then hit browse, browse out to the location and there you have it. Once you have it mapped, you can create a short cut on your desktop. or you can just make a shortcut to the folder from My network places to your desktop. Hope this helps.